Solvent extraction of tungsten from aqueous tungstate solutions

Abstract

A process for extracting tungsten values from an aqueous phase into an organic phase, comprises (a) providing an aqueous phase containing tungsten values dissolved therein, and having an initial pH of about 2.2 to about 4.0, (b) providing an organic phase depleted in tungsten and containing a secondary amine or tertiary amine extractant, a modifier, and the balance a liquid hydrocarbon solvent, (c) extracting tungsten values from said aqueous phase into said organic phase in a plurality of extraction stages operating in countercurrent fashion, and (d) recovering the organic phase enriched in tungsten values and an aqueous raffinate having a pH of about 0.3 to about 4.5.

What is claimed is: 
     
       1. A process for extracting tungsten values from an aqueous phase into an organic phase, wherein a tungsten-depleted organic extractant is mixed with a tungsten-enriched aqueous phase to form a tungsten-organic complex in said extractant, comprising (a) providing an aqueous phase containing tungsten values dissolved therein, and having an initial pH of about 2.2 to about 4.0,   (b) providing a water-immiscible organic phase selected from the group consisting of ditridecylamine dissolved in an aliphatic solvent, and water-insoluble secondary and tertiary amines dissolved in aromatic hydrocarbons, said organic phase also containing a modifier in an amount effective to increase the solubility of the tungsten-organic complex in said organic phase, and to increase the rate of separation of the organic-aqueous mixture,   (c) contacting said aqueous phase with said organic phase in a plurality of extraction stages, including a final extraction stage, operating in countercurrent fashion to extract tungsten values from said organic phase into said aqueous phase, and   (d) recovering from the final extraction stage the organic phase enriched in tungsten values and an aqueous raffinate having a pH of about 3.0 to about 4.5, wherein acid is added to the final extraction stage to maintain the pH of the aqueous raffinate at about 3.0 to about 4.5.   
     
     
       2. The process of claim 1 wherein said organic phase contains about 2 vol.% to about 20 vol.% of a secondary amine and about 2 vol.% to about 20 vol.% of nonanol or isodecanol. 
     
     
       3. The process of claim 1 or claim 2 wherein said aqueous raffinate has a pH of about 3.4 to about 4.2. 
     
     
       4. The process of claim 1 or claim 2 wherein the initial pH of said aqueous phase provided in step (a) is about 2.2 to about 3.0. 
     
     
       5. The process of claim 1 or claim 2 wherein tungsten values are extracted in step (c) in 2 to 6 extraction steps. 
     
     
       6. A process for extracting tungsten values from an aqueous phase into an organic phase, wherein a tungsten-depleted organic extractant is mixed with a tungsten-enriched aqueous phase to form a tungsten-organic complex in said extractant, comprising (a) providing an aqueous phase containing tungsten values dissolved therein, and having an initial pH of about 2.2 to about 3.0,   (b) providing a water-immiscible organic phase comprising ditridecylamine dissolved in an aliphatic solvent, said organic phase also containing a modifier in an amount effective to increase the solubility of the tungsten-organic complex in said organic phase, and to increase the rate of separation of the organic-aqueous mixture,   (c) contacting said aqueous phase with said organic phase in two to six extraction stages, including a final extraction stage, operating in countercurrent fashion to extract tungsten values from said organic phase into said aqueous phase, and   (d) recovering from the final extraction stage the organic phase enriched in tungsten values and an aqueous raffinate having a pH of about 3.4 to about 4.2, wherein sulfuric acid is added to the final extraction stage to maintain the pH of the aqueous raffinate at about 3.4 to about 4.2.   
     
     
       7. The process of claim 1, claim 2 or claim 6 wherein at least about 99.9% of the tungsten values in said aqueous phase provided in step (a) are extracted into said organic phase enriched in tungsten values. 
     
     
       8. The process of claim 1, claim 2 or claim 6 wherein said organic phase enriched in tungsten values contains at least about 40 gpl tungsten as WO 3 . 
     
     
       9. The process of claim 8 wherein said organic phase enriched in tungsten values contains at least about 75 gpl tungsten as WO 3 . 
     
     
       10. The process of claim 9 wherein said organic phase enriched in tungsten values contains at least about 100 gpl tungsten as WO 3 . 
     
     
       11. The process as described in claim 6 wherein the modifier is a long-chain alcohol having 6 to 15 carbon atoms. 
     
     
       12. The process of claim 6 wherein said organic phase contains about 2 volume % to about 20 volume % of nonanol or isodecanol.